Intraocular pressure (IOP) is a critical factor that is used to monitor the health of the eyes. High intraocular pressure (IOP) is associated with glaucoma, a leading cause of blindness. Lowering IOP is currently the only evidence-based treatment for preventing the development of glaucoma or reducing the rate of its progression.
An individual's IOP may vary significantly throughout the day. There are considerable data showing that the IOP peaks of many glaucoma patients occur outside daytime hours when IOP is usually measured. As peak IOP is related to glaucoma progression, this suggests that IOP measurements outside office hours should be taken into account when clinicians plan and prescribe glaucoma treatment. However, IOP measurements are typically conducted by professionals during eye examinations during regular business hours and only at relatively infrequent intervals, leading to a need for more accessible IOP measurement technology that provides frequently repeated IOP measurements,
The need for IOP monitoring in the population is growing rapidly as recognition of the importance of IOP control grows. Moreover, the population living with glaucoma or with raised IOP and consequently at risk of glaucoma, is growing in many countries as a result of the link between IOP and age in combination with aging populations,
To address this need, implantable pressure sensors for IOP monitoring have been proposed. For example, a microelectromechanical system (MEMS)-based passive pressure sensor was designed to be implanted inside of the anterior chamber of the eye. However, deployment of such a device presents significant challenges in requiring invasive surgery, and careful selection of its location in the eye, A micromachined capacitive pressure sensor has also been proposed, which includes circuitry that produces a phase shift in a resonant frequency to detect a change in IOP. However, this device &so requires surgery to insert the device into the anterior chamber of the eye, and specialized equipment such as an inductive coil and impedance reader must be used to obtain the phase shift information to determine IOP. A microfluidic device using a micro channel filled with gas surgically implanted in the anterior chamber of the eye was also proposed, whereby a mobile device such a smartphone could be used to take images of the aqueous humor position in the channel.
As a result less invasive approaches are desirable, One approach proposed a contact lens with a micromachined strain gauge to measure IOP. However, this design required an electrical wire connection from the strain gauge to measuring equipment. Another used a wireless ocular telemetry sensor to monitor IOP fluctuation over a 24 hour period. This sensor required sophisticated reading equipment, and only provided an indication of a fluctuation in IOP, rather than an actual measurement of the pressure. A nano-structured sensor using piezoresistive film on a contact lens has been proposed, which also required an electrical wire connection from the piezoresistor to measuring equipment. Another approach using a contact lens and telemetry detects circumferential changes in the area of the corneo-scleral junction of the eye. A flexible adhesive antenna worn around the eye wirelessly receives a signal from the contact lens, which is provided to a portable recorder, such that information is continuously acquired. Consequently, users (patients) must wear the antenna and carry a specialized electronic device for data acquisition.
Overall, the prior approaches are either invasive or require specialized electronic equipment to obtain the measurement data, which reduce the patient's comfort, and increase the complexity and cost of clinical implementation.